This invention relates, in general, to plant growth regulation, especially to horticultural plant growth regulation and, in particular, is directed to chemical compositions for regulating the growth of turf grasses.
The maintenance of established lawns may involve the application of fertilizer two or three times a year, usually during the growing season, and frequent mowing of the grass. In general, the healthier the lawn grasses, the faster the growth and the more frequently the grass must be cut in order to retain its healthy condition and attractive appearance. Thus, the typical home owner is confronted with the time consuming and, at times, arduous task of mowing the lawn at least once and usually twice every ten days during the growing season. During ideal weather conditions, including plentiful rainfall, the grass may have to be mowed even more frequently in order to maintain its vigorous condition and presentable appearance.
The prior art has long recognized the need for a practical method for inhibiting the vertical growth of turf grasses without impairing the general health of the grass. Still more desirably, there has been a long felt need for a growth regulating composition which is capable of effecting a reduction in vertical growth, while at the same time, promoting lateral growth. Although many chemical agents have previously been suggested for application to lawns for this two-fold purpose, that is, of regulating the vertical and horizontal growth of grass while not impairing the general health thereof, no known growth regulator or combination thereof has apparently been successful in attaining this two-fold goal.
Maleic hydrazide has been reported as early as 1949 to have the capability of inhibiting the growth of plants without killing them. It is reported to act as a mytotic poison and, as such, to stop normal cell division in susceptible plants. Accurate dosage of maleic hydrazide has been determined to be very critical and, since broadleaf plants are less affected by the compound, one or two applications of a slight overdose usually results in the lawn grasses tending to die and the weedy species to predominate; for these reasons, it is seldom used to retard the growth of fine turf grasses.
In the early 1960's, a group of chlorinated and fluorinated carboxylic acid compounds was determined to cause morphological changes in plants. These compounds bring about morphological changes in plants considerably more slowly and with a lack of persistence compared with other synthetic regulators such as maleic hydrazide and are given the characterizing group designation of "Morphactins." The methyl esters of three of the compounds --methyl-2-chloro-9-hydroxy-fluorine-9-carboxylate, methyl-9-hydroxyfluorine-9-carboxylate, and methyl-2, 7-dichloro-9-hyroxyfluorine-9-carboxylate-- are currently employed in combination as the active plant growth regulating ingredients in a commercial formulation to control seed head formation in weedy annual bluegrass and, in combination with maleic hydrazide, are suggested as growth retarding agents for turf grasses and weeds, primarily for roadside and golf course maintenance.
In 1969, McVey (U.S. Pat. No. 3,462,257) disclosed the use of 6-azauracil in combination with a nitrogen-containing fertilizer and other essential plant nutrients as a plant growth regulating composition for effectively retarding the growth of turf species. Since the azauracils are chemical analogs of the nucleic acid constituents, thymine and uracil, they quite possibly inhibit the growth of turf grasses by interfering with the replication of nucleic acids. As such, they may also have similar negative effects in animals, and thus, may be potentially hazardous to humans and pets during and after applications to lawns.
More recently, Harrington et al., in U.S. Pat. No. 3,639,474 have disclosed 5-acetamido-2-methyltrifluoromethanesulfonanilide, also termed 3-trifluoromethylsulfonamido-p-acetotoluidide, as being particularly active in the control of tobacco suckers and retardation of growth of some plants, including grass species, without significant distortion of the normal foliar shape. The 3M Company, St. Paul, Minn., assignee of the patent, has marketed 3, trifluoromethylsulfonamido-p-acetotoluidide in a diethanolamine salt form under the name of "Sustar". According to the 3M Company, several turf grasses have exhibited excellent vegetative growth inhibition and seed head suppression, after application of "Sustar" at the recommended rates. Occasional slight discoloration of short duration has also been evident and top growth inhibition lasting from four to six weeks has been induced from a single application.
Also in 1969, Fritz et al. patented (Canada No. 803,947) a plant growth regulation process utilizing phosphoric compounds. Amchem Products, Inc., Ambler, Pennsylvania, the assignee of the patent, has commercialized at least one of the phosphoric compounds; namely, 2-chloroethyl-phosphonic acid under the trade name "Ethrel" known otherwise as ethephon. According to the patent, many of the phosphonic compounds, including 2-chloroethyl-phosphonic acid (Ethrel) have demonstrated commercial use and growth regulating properties including the inducement of sprouting of underground buds of monocotyledonous plants and, in many cases, growth stimulation at one or more of the customary growth sites to affect increase yields of fruit by control of apical dominance.
Although many investigations have been made toward the development of the vertical growth inhibitors for turf grasses, apparently none of the products from these inventigations has met with wide consumer acceptance for use on residential lawns and none is known to be presently commercially available for such purpose. The present invention is, therefore, directed to an improved and comparatively safe and reliable method for inhibiting the vertical growth of turf grasses and promoting the lateral growth of the same without impairing the health of the grass; that is, without substantially affecting the color of the grass or the appearance of the blade itself. This invention makes possible a significant reduction in the frequency of mowing necessary to maintain turf grasses in a healthy and attractive appearing condition. As such, the invention has provided a satisfactory solution to the heretofore long felt but unresolved need for safe, effective, and reliable growth-regulating agents for turf grasses capable of maintaining at the same time, the healthy appearance of the grasses.